OBJECTIVES: 1. Efforts will be made to purify and identify two growth factors that, along with insulin, are required by chick embryo fibroblast for progression through the G1 period. 2. Studies on the mechanism of stimulation of non-cationic chick embryo fibroblast polypeptides by insulin and translational inhibitors will be pursued. 3. The mechanism by which serum, but not insulin, stimulates the synthesis of a chick embryo fibroblast polypeptide (pp. 41) will be explored. 4. Broad post-transcriptional changes in RNA metabolism will be sought in resting baby hamster kidney cells after stimulation with serum.